Libertarians believe that individuals should be allowed to pursue their own interests, unless their behavior impacts the interests of others, especially if it negatively impacts others. So individuals should be allowed, according to this view, to buy the food they want, whereas drunk drivers should be constrained because they harm others, and chemical producers should be prevented from polluting as much as they would choose because their pollution hurts children and adults.
Modern research argues that sometimes individuals may not have enough information to effectively pursue their interests. In these cases, it may be suggested that government regulations and rules help guide individuals to the better pursuit of interests they would have if they had additional information. A few weeks ago Posner and I debated the role of information in interpreting New York City's recently enacted ban on the use of trans fats in restaurants.